The present invention relates to a true graft copolymer composition containing low or high vinyl butadiene grafted onto substituted polyacrylates and a method for making the same. More specifically, the present invention relates to free flowing molding or powdered compositions containing high vinyl polybutadiene grafted onto the backbone of a substituted polyacrylate through anionic polymerization.
Heretofore, high vinyl polybutadiene thermosetting resins although having outstanding electrical properties nevertheless possessed several shortcomings such as poor impact resistance and poor coldflow properties. A previous approach to eliminate these disadvantages involved the preparation of copolymers containing styrene but was unsuccessful since the benzylic hydrogens in the styrene segments retard the cure of the resin in much the same manner as allylic hydrogens in 1,4-butadiene retard cure.
Moreover, prior anionic polymerization of substituted acrylates such as methyl methacrylate were generally difficult and unpractical due to problems with side reactions and hence polymerization has been according to the free radical route.
Waack, U.S. Pat. No. 3,235,626 granted Feb. 15, 1966 relates only to copolymers prepared through free radical polymerization.
Griffith et al., U.S. Pat. No. 3,803,265 granted Apr. 9, 1974 relates to a free radical reaction wherein butadiene is incorporated into a methyl methacrylate chain and thus forms a copolymer.
Milkovich et al., U.S. Pat. No. 3,786,116, granted Jan. 15, 1974, relates to a copolymer backbone having a third polymer grafted thereto. Should a free radical mechanism be utilized, a gel will form due to the existance of free double bonds which permit cross-linking between polymers or chains. If anionic polymerization is utilized, a highly branched polymer is formed. A cationic reaction does not take place if butadiene is utilized. Additionally, the graft copolymer of Milkovich is not attached to the backbone through a carbonyl or ketone group.
O'Neill, U.S. Pat. No. 3,636,141, granted Jan. 18, 1972, basically relates to prevention of shrinkage of high vinyl polybutadiene compounds. Methyl methacrylate polymers as well as polymers produced from vinyl monomers are utilized merely as fillers. Should polybutadiene be utilized, the free radical mechanism of O'Neill will result in cross-linking.